/Engine/Source/Runtime/Engine/Classes/Sound/SampleBufferIO.h
This writes out the InSampleBuffer as a wav file at the path specified by FilePath and FileName. If FilePath is a relative path, it will be relative to the /Saved/BouncedWavFiles folder, otherwise specified absolute path will be used. FileName should not contain the extension. This can be used in non-editor builds.
bool BeginWriteToWavFile ( const [TSampleBuffer](API\Runtime\SignalProcessing\TSampleBuffer)<> & InSampleBuffer, const [FString](API\Runtime\Core\Containers\FString) & FileName, [FString](API\Runtime\Core\Containers\FString) & FilePath, [TFunction](API\Runtime\Core\GenericPlatform\TFunction)< void()> OnSuccess )